Merged LiFeYPO4 1000Ah Winston prismatic cells and all electric galley...

[JuliaYu]

Originally Posted by YARGESOL

I'm in the process of rebuilt and,since ev-power has 1000Ah fully booked for 1/2 year, I hesitating - to take 700Ah, or parallel them to 1400Ah.

Hi Yargesol, we have Winston 1000Ah cells can ship to you within one week, well matched cells ship from Winston factory directly. There are few members purchased from me already. PM me or email me via sales@skypowerintl.com if you are interested. Thanks.

[CatNewBee]

Originally Posted by YARGESOL

Hi,CatNewBee! Do you know, how much Your induction cooktop eats per day?
I'm in the process of rebuilt and,since ev-power has 1000Ah fully booked for 1/2 year, I hesitating - to take 700Ah, or parallel them to 1400Ah.
There are some warnings on the web & here for the large size cells (more than 200Ah not reccomended for marine use) . Your own experiance showes opposite ?

Hard to tell, we use so many appliances for various things. The induction hob is a small part of our daily energy consumption. I would guess in average 0.6..1kWh, maybe.

It depends on what you are cooking and for how long.

Regarding the cell size. I dont know actually if a lot small cells would be any better. They need to be fixed too and it as a lot more movement and connectors.

I have the cells in the port aft cabin under the bed where the original batteries were, this is the most neutral place on the cat in heavy seas. The 4 cells weight about 170kg (42kg per celll and are fixed to the plank and the side, very well secured, I use double bridges per cell made of solid copper 30mm x 5mm crossection. The whole thing is really rigid. No issues whatsoever. I could probably fit 4x700Ah, but not 8x700Ah there. It depends on your space and geometry what you can fit. 700Ah would work too, I rarerly discharge more than 600Ah anyway. But I like to have spare energy.

If you opt for the 700Ah cells, you can start with 4 and add later the next 4 if you feel the need. In general it is better to have equal cells from the beginning, but you can also add the next 4 as a separate battery with an own bms if they are too different.

[YARGESOL]

Thank,CNB. On my cat the quitest place is amidship-center salon. Here commes anyone,if suffer offshore. The bank is right below the seat. I may accomodate 8 cells 700Ah-counts to 536mm-without gap under the bench. I'll probably start with 700Ah. I like your setup of electric gallee-no heat exhaust in the summer,no hassle with bottles. Thought,out of season,I may heat up salon with a gas cooker...But,I gonna fix Webasto for that purpose

[CatNewBee]

UPDATE:

Today I have done a capacity test to check the battery health, but I did not go down to 0 SOC, the goal was to see what I can draw safely with high current inverter use und if my charge regime with solar and daily full battery over now 2 years of usage.

So I stopped the test after 1000Ah drawn (the nominal cell capacity), did not go down to 1200Ah as in my first test, just to not stress the battery too much. Test was performed with 230..250A continous discharge at 3000W.

See pictures attached, cell voltages under load 3.147...3.129V, without load after the test, 3.182...3.172V, BMS was far from disconnecting the inverter (set to 3.050V) and LVP at 2.900V. I assume there was still 200Ah life in the cells.

So very happy with the Winston cells.

Some battery statistics in the screenshots. (cycles, syncs, total energy charged and discharged over the lifetime)

[newhaul]

Originally Posted by CatNewBee

UPDATE:

Today I have done a capacity test to check the battery health, but I did not go down to 0 SOC, the goal was to see what I can draw safely with high current inverter use und if my charge regime with solar and daily full battery over now 2 years of usage.

So I stopped the test after 1000Ah drawn (the nominal cell capacity), did not go down to 1200Ah as in my first test, just to not stress the battery too much. Test was performed with 230..250A continous discharge at 3000W.

See pictures attached, cell voltages under load 3.147...3.129V, without load after the test, 3.182...3.172V, BMS was far from disconnecting the inverter (set to 3.050V) and LVP at 2.900V. I assume there was still 200Ah life in the cells.

So very happy with the Winston cells.

Some battery statistics in the screenshots. (cycles, syncs, total energy charged and discharged over the lifetime) Attachment 205070Attachment 205071Attachment 205072

Excellent post sounds like you are still well above the spec ah for your bank. Thanks for the post and shots of your meters .

[nebster]

Looking good!

That SOC estimation versus voltage and current matches my observed values almost exactly.

Do you set your BMV capacity a little lower than the true tested capacity?

Is the 47 total charge cycles accurate for your battery lifetime? (Your pack has been in service for ~19 months?)

Why does your BMV show 62 syncs and only 47 charge cycles? That seems weird, to get syncs without charging sometimes.

[CatNewBee]

Originally Posted by nebster

Looking good!

That SOC estimation versus voltage and current matches my observed values almost exactly.

Do you set your BMV capacity a little lower than the true tested capacity?

Is the 47 total charge cycles accurate for your battery lifetime? (Your pack has been in service for ~19 months?)

Why does your BMV show 62 syncs and only 47 charge cycles? That seems weird, to get syncs without charging sometimes.

Yes the SOC readings, this is my fault, not of the instruments.

I had set the REC ABMS at the beginning to 1200Ah, the measured initial capacity to have an exact reading, the BMV battery capacity I set to 1100Ah, for two reason, one was I wanted to have a 100% full status at 95% of the real battery capacity, and later noticed, if you change the battery capacity, victron resets the history assuming it is a new battery, I dont want to lose the history, so I live with this.

Anyway, the Victron gauge is set to show the Ah counter, the REC gauge has a prominent SOC in percent, so both are the right readings on the panel.

Victron considers a cycle only if you go below a certain SOC, shallow charges and discharges are not counted.

Synchronizations happen only if you reach the programmed voltage and if it stays there for a while with the trailing amps below a set value, this is seldom reached and independent of charge cycles counter. It is set at the moment to 14.2V or the Ah counter gets to 0Ah and this voltage is only hit by the solar controller when it gets to float. It happens not very often, we use energy during the day and consume what comes in.

According to the total counters, 99000Ah are drawn, so it equals for me to 99 full discharges and charges, I would say 99 full cycles (or 200 to 50% discharge cycles? ).

[john61ct]

Great result, funny how a 250A continuous draw doesn't break a sweat, only 0.25C, benefit of an oversized bank, will also pay off in extra longevity.

Did you note the lowest voltage toward the end under that load?

That 8% is likely to be realistic, when you say you think 200Ah left, I think not usable, and as you say better not to even test for it more often than needed, say every other year maybe.

In fact the bank is still "new enough", you can create your own gentler but still pretty precise Ah capacity test parameters, e.g. from (whatever definition of) Full

down to 3.0V either (ideally) resting or at that standard discharge rate.

Even using an Ah counter rather than timing a precisely held CC load, long as you keep everything the same, a valid benchmark.

Even if you are only losing under 1% capacity per year of use, if that rate grows in future years that's valuable information.

[newhaul]

Originally Posted by john61ct

Even if you are only losing under 1% capacity per year of use, if that rate grows in future years that's valuable information.

where are you getting this loss of capacity in his bank ?

[john61ct]

I'm talking about empowering yourself to find out what the actual rate is, through objective testing.

Most people apparently feel doing so is not worth the trouble, I know.

I was just using that as a hypothetical rate, as should be clear from the phrase "even if".

[nebster]

Originally Posted by CatNewBee

I had set the REC ABMS at the beginning to 1200Ah, the measured initial capacity to have an exact reading, the BMV battery capacity I set to 1100Ah, for two reason, one was I wanted to have a 100% full status at 95% of the real battery capacity, and later noticed, if you change the battery capacity, victron resets the history assuming it is a new battery, I dont want to lose the history, so I live with this.

That makes sense. I have a similar "derating" employed.

Victron considers a cycle only if you go below a certain SOC, shallow charges and discharges are not counted.

I think it is {go below 65%, then above 90%}. You must be getting lots of shallow discharges (or incomplete charges). Total Ah is probably the more useful number anyway.

[Synchronization] happens not very often, we use energy during the day and consume what comes in.

So, have you noticed your BMV SOC drifting away from your Rec SOC when you have long periods without a sync? If so, have you been able to zero in on any changes to peukert/charge eff on the BMV to try to get them closer together?

I've played with mine a bit, but I still wonder if there is room to improve it.

[john61ct]

What is the basis for reckoning the BMS is the more accurate SoC guesstimator?

[nebster]

Originally Posted by john61ct

What is the basis for reckoning the BMS is the more accurate SoC guesstimator?

Just that it looks dead-on to me, and my experience is that I can be more accurate with pen and paper than a drifting integrator (like the BMV) is, if current is reasonably stable for a little while and I have a lookup table in front of me.

I assume Rec selected an algorithm that takes advantage of this -- perhaps a chemistry-specific function over voltage and current, plus compensation based off of current integration.

A hybrid of these two estimation techniques probably gets most of the way there without having to employ any exotic math (and perhaps without any of the crazy results we see from the under-constrained ML approach that another vendor appears to be using).

Just a guess, though.

[CatNewBee]

Well, not too bad, the Ah counters are in sync, maybe about 10..20Ah off due to different sync points and zero Amp calibration, but stable over a long time.

The SOC percentage is off due to the different settings for the battery size, but consistent. At 1002 Ah drawn the one shows round 8% based on 1100Ah and the other about 19% based on 1200Ah and a count of 1007Ah, if you look at the screenshots.

So both are right.

The formula how it is calibrated (shunt) is in the REC manual, you can tweak it if you want to. Also the gain settings and the voltage resolution of the ADC, the charge algorithm among others.

What was also important to my setup was a tweaking of the aggregation filter, they filtered by default 50,60,100 and 120Hz interferences, but the Quattro uses other internal frequencies, what interferred with the BMS sampling causing jumping measurements on the cell voltages under load/charge, so Tine from REC adjusted the sampling rate on my firmware to mitigate this, it was at the beginning as I bench tested the setup. It is great to have the contact to the developer, amazing service from REC!

They still have the same company spirit and help with customizations if requested.

[nebster]

Originally Posted by CatNewBee

Well, not too bad, the Ah counters are in sync, maybe about 10..20Ah off due to different sync points and zero Amp calibration, but stable over a long time.

I'm amazed. In your example (from your test), though, you are not that far away from a sync. I'm seeing the error accumulate over longer periods - say, two weeks without a sync to 100%.

Do you also see your BMV staying accurate at that point?

The formula how it is calibrated (shunt) is in the REC manual, you can tweak it if you want to. Also the gain settings and the voltage resolution of the ADC, the charge algorithm among others.

Cool. I just pulled a manual, but it only has a general description of the formula. It alludes to their using both an integrator and a voltage/current lookup, though, which rings true to me.

What was also important to my setup was a tweaking of the aggregation filter, they filtered by default 50,60,100 and 120Hz interferences, but the Quattro uses other internal frequencies, what interferred with the BMS sampling causing jumping measurements on the cell voltages under load/charge, so Tine from REC adjusted the sampling rate on my firmware to mitigate this, it was at the beginning as I bench tested the setup. It is great to have the contact to the developer, amazing service from REC!

Interesting. That is cool!

Unfortunately for me, tuning a third-party BMS' integrator is not the problem I have. I want to tune the Victron BMV further. Maybe there is something to this sampling interference issue, though. Hmm.